Functional characterization of cAMP signaling of variant porcine MC1R alleles in PK15 cells

Abstract

Summary The melanocortin 1 receptor (MC1R), encoded by the classical extension (E) coat color locus, is expressed on the surface of melanocytes and plays a critical role in switching melanin synthesis from pheomelanin (red/yellow) to eumelanin (black/brown). Different MC1R alleles associated with various coat color patterns in pigs have been identified over the past decades. However, functional analysis of variant porcine MC1R alleles has not yet been performed. Therefore, in this study, we examined the subcellular localization and cyclic adenosine monophosphate (cAMP) signaling capability of MC1R variants in porcine kidney epithelial cells (PK15) overexpressing different MC1R alleles. Transcriptional slippage may partially restore the reading frame of the EP allele, possibly accounting for the observed spot phenotype. The A243T substitution in the e allele severely disrupted the membrane localization of the MC1R receptor, resulting in a severely impaired cAMP signaling capability. Both the V95M and L102P substitutions in the ED1 allele may contribute to the constitutively active function of MC1R, thus accounting for the dominant black phenotype. The D124N substitution in the ED2 allele severely attenuated the cAMP signaling capability of MC1R; however, whether this mutation contributes to the distinct phenotype of Hampshire pigs requires further investigation. Thus, our results provide new insights into the functional characteristics of MC1R variants and their roles in porcine coat color formation.

Pig Coat Color Manipulation by MC1R Gene Editing

“…Of them, mutations at positions 95 and 102 are considered to be the specific common variations in Chinese indigenous black pigs [ 12 ]. V95M and L102P substitutions in the E D1 allele may contribute to the active function of MC1R, thus accounting for the dominant black phenotype [ 13 ]. A164V and A243T are the specific missense mutations in the Duroc breed.…”

“…A164V and A243T are the specific missense mutations in the Duroc breed. A243T is believed to substantially disrupt MC1R function, resulting in a red coat color phenotype of Duroc pigs [ 9 , 13 ].…”